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Vol. LXIII, No. 1
January 7, 2011

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Not All Soy Created Equal
Researcher Barnes Offers Compelling Reasons to Eat Soy
Dr. Stephen Barnes

Oh, to be young again…This is probably what many attendees of a recent lecture given by Dr. Stephen Barnes of the University of Alabama at Birmingham were thinking.

The lecture, last fall’s installment in NCI’s Stars in Nutrition and Cancer seminar series, brought a healthy crowd to Lipsett Amphitheater to hear about soy as nutrition, soy as cancer preventive and the chemical makeup of soy, which, as it turns out, is fairly extensive.

For all the hubbub about soy—is it good?, is it bad?—the general consensus in the scientific community, according to Barnes, is that this plant-based protein can prevent breast cancer in women, but it may depend on how much soy a woman has eaten before, say, her teenage years, and what kind. Current research is now exploring soy’s potential to ward off prostate cancer in men. And while beneficial if eaten at any age, soy’s positive influence seems to pack a greater punch if included as part of a lifelong diet.

“Soy has been around for a long time,” Barnes said, noting records that show the Chinese have been eating it since 2800 B.C. Soy’s presence in the west, however, came much later.

“In 1765, it was introduced to the U.S. in Savannah [and later used as] a coffee alternative during the Civil War,” he said.

Since then, soy has been used for everything from biofuel, inks and candles to plastics, insulation and clothing. And, of course, food. Though the U.S. is now the world’s largest producer of soy and exports much of it to Asian nations, soy has yet to find its way into the regular diets of Americans.

“Not all soy is the same,” Barnes cautioned. “And not all soy is soy.”

“Not all soy is the same,” Barnes cautioned. “And not all soy is soy.”

Barnes said that while Asians consume anywhere between 10 to 50 grams of soy daily (and even higher on the island of Okinawa where the oldest of Japanese live), Americans might only get 1 to 2 grams every day, and much of that may come indirectly. Though tofu and edamame (green soybeans in the pod) are available at most grocery stores, soy often shows up in our shopping carts in a completely different form: in the steaks, pork chops and chicken wings that we buy after those farmed animals have eaten a diet including soy. For us, that doesn’t amount to much of the beneficial compounds.

“Soy is not a chemical substance, it’s a plant. A plant cannot run away from its predators so it’s a very adaptable chemical factory. One of the chemicals is the isoflavones,” said Barnes, naming one of the collection of beneficial compounds in soy. However, Barnes warned researchers hoping to use soy that not all soy is created equal.

“This collection [of compounds] is not constant and varies with the strain of the soybean—where it’s grown and when it’s harvested, rather like a wine,” he said. Consumers are exposed to a range of soy products that come from a variety of origins.

Barnes also said trying to compare the soy found in Asian diets versus American diets would be like comparing apples to oranges. In Asia, many soy products are fermented variations of the protein, whereas they are often not fermented in the U.S. While U.S. food manufacturers include soy proteins containing isoflavones in their products, their processing alters the chemical composition.

“Not all soy is the same,” Barnes said. “And not all soy is soy.”

Still, soy stands to wield great influence on cancer prevention efforts in the U.S., Barnes said, noting that this country unfortunately has one of the highest rates of breast cancer in the western world. While it can’t help that Americans tend to eat more foods high in fat, salt and empty calories, Barnes said higher rates of cancer and obesity may have more to do with what people aren’t putting on their plates.

“It’s the absence of preventive agents that is more harmful, not what people are eating,” he said. Not only are people not replacing fattier protein sources with something kind to the body like soy protein, they’re not getting the beneficial effects they could from foods based in soy. He’d like to see that change.

“Prevention is probably how we can lick cancer in the first place rather than fixing it once it’s arrived,” he said. NIHRecord Icon

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